Sounds like you bought a used BlackBerry and the old owner didn't let everyone on his BBM contact list know he had a new device with a new PIN. This mystery contact still had the old owner in his/her address book, but with the old PIN. They saw the old contact was gone from their BBM and sent you an invite, thinking they were re-adding the old owner. I've gotten PIN messages from folks who didn't know I was the new owner of a used BlackBerry and thought they were messaging the old owner. Some interesting stuff came through too! Internal numbers on a pending deal, and a comment or two on last night's pub crawl. Good stuff!